1. Field of the Invention
The present invention is in the field of compression bonded discrete semiconductor devices.
2. Description of the Prior Art
Compression bonded semiconductor devices are generally well known in the art.
The use of protective coating on at least the edge portions of bodies of semiconductor material is also generally well known.
The insulating protective coating on the edge of the semiconductor body serves to protect the pn-junction or the pn-junctions which occur at the semiconductor's edge, such junctions being very sensitive to external influences such as, for example, moisture. The insulating protective coating is of very great importance as far as the functioning of the semiconductor component is concerned because, when loading in the blocking direction, the properties of the semiconductor component are primarily determined by processes which take place at the semiconductor's periphery.
Employing lead electrodes with a ridged surface is also known in the prior art. The purpose of the ridges on the known types of semiconductor devices, and which are produced, for example, by a specific roughening of the contact faces by lapping, is to improve the contact between the lead electrodes and the body of the semiconductor material. In addition, ridges and the attendant grooves make it possible to balance out the different thermal expansion coefficients of the lead electrodes and of the semiconductor material in the direction of the main surfaces of the semiconductor body. A semiconductor device has also been described in the prior art, one lead electrode of which is provided with ridges which consist of a metal which alloys with the electrode on the body of semiconductor material. In this case, the purpose of the ridge is to so raise the pressure exerted on the semiconductor element's electrode that a diffusion alloy is soon produced at the operating temperature of the semiconductor device. By this means, there is produced a positive bond between the lead-electrode and the semiconductor without any special alloying process.
In the case of semiconductors having a relatively large surface area, such as, for example, 20 mm.sup.2 and above, it is a relatively simple matter to apply the insulating protective coating to the semiconductor's edge, it being possible to carry out such a process semi-automatically. However, the application of the insulating protective coating to the semiconductor's edge is an intricate and wasteful process in the case of semiconductors having an area of only a few mm.sup.2.
Attempts have been made in the past to coat not only the edges of small bodies of semiconductor materials, i.e., 15 mm.sup.2 and less, but also the opposed major faces of the bodies. It will be understood that in coating the opposed major faces, the coating was applied over the metal electrodes affixed to the major faces.
These attempts have not been successful since it was then impossible to establish good electrical contact between the metal electrodes and the lead electrodes.